This invention relates to a driving device for use in combination with a Bloch line memory device and, in particular, to a driving device for propagating each of Bloch line pairs in the Bloch line magnetic memory device.
A Bloch line memory device is proposed in the copending U.S. patent application Ser. No. 542,963 filed on Oct. 18, 1983 by Susumu Konishi et al and now U.S. Pat. No. 4,583,200. The memory device has a bit capacity which is as high as 1.6 gigabits/cm.sup.2. Consideration is therefore made about application of the memory device to a file memory of a computer and to a memory decoder on board a spacecraft.
In a Bloch line memory device, each of Bloch line pairs should successively or stepwise be propagated in the memory device from a write-in position to a read-out position. For this purpose, an inductor element or coil is disposed in the vicinity of the memory device to generate a magnetic field parallel to the Bloch line pairs.
More specifically, the magnetic field must drastically be varied within a short time interval of, for example, 20 nanoseconds over a wide range. The range may be, for example, 20 Oe. Otherwise, each Bloch line pair does not begin to propagate in the memory device.
In order to propagate each Bloch line pair from an original position to an adjacent position, the inductor element is supplied from a driving circuit with a succession of driving pulses, each of which has a rise time of 20 nanoseconds from a leading edge thereof. In this event, an electric voltage must be 500 volts. Therefore, the driving device is impractical.
Let each Bloch line pair be propagated by the use of the above-mentioned driving device from the original position to the adjacent one during the rise time and each of the driving pulses have a fall time equal to the rise time. Under the circumstances, each Bloch line pair returns back to the original position from the adjacent one because the magnetic field is also rapidly varied during the fall time of each driving pulse.
Such return of the Bloch line pairs can be avoided by elongating the fall time of each driving pulse so as to slowly reduce the magnetic field. For example, the fall time is about 50 times as long as the rise time. This means that the driving pulse succession should have a low repetition frequency and each Bloch line pair is slowly propagated from the write-in position eventually to the read-out position.